Epidemiologic programs for computers and calculators. Exact binomial confidence intervals for the relative risk in follow-up studies with sparsely stratified incidence density data.

The authors present a computer program for hypothesis testing and calculation of exact binomial confidence intervals for the adjusted relative risk in follow-up studies involving multiple strata with incidence density (person-time) denominators and small or zero person-count numerators. The program is an extension to multiple tables of a single-table method by Rothman and Boice (NIH publication no. 79-1649, Washington, DC: US GPO, 1979) and represents a counterpart for person-time denominators to the program of Thomas (Comput Biomed Res 1975;8:423-46) for exact analysis of multiple tables with person-count denominators. Comparisons with asymptotic analyses of real and simulated data are given. Copies of the program are available from the authors on request.